Local magnetic susceptometry : Visualizing functional properties of novel materials

Abstract: One of the rapidly growing instrumentation technologies of late has been Surface Probe Microscopy. Since the award of the Nobel Prize in 1986, this form of instrumentation has expanded into various fascinating forms and is successfully enabling investigations at a nano-scale. A particular type of SPM method, Magnetic Force Microscopy, (MFM) enables visualization of magnetic domain structures of various materials at several nano to micron scale. However, obtaining quantitative information about magnetic properties of materials is difficult since this method is cantilever tip-surface interaction dependent and calibration is not straightforward. The purpose of this thesis work is to fill the gap, and exploit it to investigate many functional properties of novel materials. Experimental development takes time and if it is to be patented, then clearly no public disclosures on related studies are possible until the patents have been filed. Thus this thesis contains the following as yet unpublished work.:• Invention of a new Sensor Head and development of the next generation Desk-top Local Magnetic Susceptometer (DLMS) Reasonable description of the sensor head and its operation are included in this section – more details not included in this thesis are a part of the US Patent Document (Filed on May 27, 2005.) The DLMS instrumentation is one of its kind and there exists no commercial equivalent today.• Demonstration of the applications of above new DLMS to investigate local magnetic phenomena in a variety of advanced materials like:1) First observation of Deformation induced Ferromagnetism, DILM, in Iron Aluminide sheets. We know of no other material which exhibits this unique property of developing local ferromagnetism upon deformation. ..more details than in the thesis are a part of the US Patent application entitled ‘Iron Aluminde Readable Medium’ (Filed on May 27, 2005.)2) Micro-indentation and its consequence on the local magnetic properties, with magnetic imaging of the local structure of these indents in the Iron Aluminide Sheets in the thickness range 180 to 200 ?m.3) Strain induced dislocations, their propagation, formation of magnetic precipitates of phase separated compounds in high performance Stainless Steel, and even the development of martensitic transformations in cast steels (in collaboration with Prof. Takagi at Tohoku University).4) Monitoring magnetic particles and aggregates and their evolution in space and time from targeted drugs labelled with magnetic particles;5) Invention of a method to develop patterned ferromagnetic entities in flexible Kapton and imaging the local magnetic structure – study towards the media enabling future transparent electronics• In addition following studies have been carried out and reported:1) Tailored Bulk Glassy material to produce materials with unusually high mechanical hardness property known so far in any metallic system, and2) A comparison of Physical Properties of melt-spun and bulk glassy materials3) The co-existence of Superconductivity and Ferromagnetism in NiBi alloys.